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+/*++
+/* NAME
+/* scache_multi 3
+/* SUMMARY
+/* multi-session cache
+/* SYNOPSIS
+/* #include <scache.h>
+/* DESCRIPTION
+/* SCACHE *scache_multi_create()
+/* DESCRIPTION
+/* This module implements an in-memory, multi-session cache.
+/*
+/* scache_multi_create() instantiates a session cache that
+/* stores multiple sessions.
+/* DIAGNOSTICS
+/* Fatal error: memory allocation problem;
+/* panic: internal consistency failure.
+/* SEE ALSO
+/* scache(3), generic session cache API
+/* LICENSE
+/* .ad
+/* .fi
+/* The Secure Mailer license must be distributed with this software.
+/* AUTHOR(S)
+/* Wietse Venema
+/* IBM T.J. Watson Research
+/* P.O. Box 704
+/* Yorktown Heights, NY 10598, USA
+/*--*/
+
+/* System library. */
+
+#include <sys_defs.h>
+#include <unistd.h>
+#include <stddef.h> /* offsetof() */
+#include <string.h>
+
+/* Utility library. */
+
+#include <msg.h>
+#include <ring.h>
+#include <htable.h>
+#include <vstring.h>
+#include <mymalloc.h>
+#include <events.h>
+
+/*#define msg_verbose 1*/
+
+/* Global library. */
+
+#include <scache.h>
+
+/* Application-specific. */
+
+ /*
+ * SCACHE_MULTI is a derived type from the SCACHE super-class.
+ *
+ * Each destination has an entry in the destination hash table, and each
+ * destination->endpoint binding is kept in a circular list under its
+ * destination hash table entry.
+ *
+ * Likewise, each endpoint has an entry in the endpoint hash table, and each
+ * endpoint->session binding is kept in a circular list under its endpoint
+ * hash table entry.
+ *
+ * We do not attempt to limit the number of destination or endpoint entries,
+ * nor do we attempt to limit the number of sessions. Doing so would require
+ * a write-through cache. Currently, the CTABLE cache module supports only
+ * read-through caching.
+ *
+ * This is no problem because the number of cached destinations is limited by
+ * design. Sites that specify a wild-card domain pattern, and thus cache
+ * every session in recent history, may be in for a surprise.
+ */
+typedef struct {
+ SCACHE scache[1]; /* super-class */
+ HTABLE *dest_cache; /* destination->endpoint bindings */
+ HTABLE *endp_cache; /* endpoint->session bindings */
+ int sess_count; /* number of cached sessions */
+} SCACHE_MULTI;
+
+ /*
+ * Storage for a destination or endpoint list head. Each list head knows its
+ * own hash table entry name, so that we can remove the list when it becomes
+ * empty. List items are stored in a circular list under the list head.
+ */
+typedef struct {
+ RING ring[1]; /* circular list linkage */
+ char *parent_key; /* parent linkage: hash table */
+ SCACHE_MULTI *cache; /* parent linkage: cache */
+} SCACHE_MULTI_HEAD;
+
+#define RING_TO_MULTI_HEAD(p) RING_TO_APPL((p), SCACHE_MULTI_HEAD, ring)
+
+ /*
+ * Storage for a destination->endpoint binding. This is an element in a
+ * circular list, whose list head specifies the destination.
+ */
+typedef struct {
+ RING ring[1]; /* circular list linkage */
+ SCACHE_MULTI_HEAD *head; /* parent linkage: list head */
+ char *endp_label; /* endpoint name */
+ char *dest_prop; /* binding properties */
+} SCACHE_MULTI_DEST;
+
+#define RING_TO_MULTI_DEST(p) RING_TO_APPL((p), SCACHE_MULTI_DEST, ring)
+
+static void scache_multi_expire_dest(int, void *);
+
+ /*
+ * Storage for an endpoint->session binding. This is an element in a
+ * circular list, whose list head specifies the endpoint.
+ */
+typedef struct {
+ RING ring[1]; /* circular list linkage */
+ SCACHE_MULTI_HEAD *head; /* parent linkage: list head */
+ int fd; /* cached session */
+ char *endp_prop; /* binding properties */
+} SCACHE_MULTI_ENDP;
+
+#define RING_TO_MULTI_ENDP(p) RING_TO_APPL((p), SCACHE_MULTI_ENDP, ring)
+
+static void scache_multi_expire_endp(int, void *);
+
+ /*
+ * When deleting a circular list element, are we deleting the entire
+ * circular list, or are we removing a single list element. We need this
+ * distinction to avoid a re-entrancy problem between htable_delete() and
+ * htable_free().
+ */
+#define BOTTOM_UP 1 /* one item */
+#define TOP_DOWN 2 /* whole list */
+
+/* scache_multi_drop_endp - destroy endpoint->session binding */
+
+static void scache_multi_drop_endp(SCACHE_MULTI_ENDP *endp, int direction)
+{
+ const char *myname = "scache_multi_drop_endp";
+ SCACHE_MULTI_HEAD *head;
+
+ if (msg_verbose)
+ msg_info("%s: endp_prop=%s fd=%d", myname,
+ endp->endp_prop, endp->fd);
+
+ /*
+ * Stop the timer.
+ */
+ event_cancel_timer(scache_multi_expire_endp, (void *) endp);
+
+ /*
+ * In bottom-up mode, remove the list head from the endpoint hash when
+ * the list becomes empty. Otherwise, remove the endpoint->session
+ * binding from the list.
+ */
+ ring_detach(endp->ring);
+ head = endp->head;
+ head->cache->sess_count--;
+ if (direction == BOTTOM_UP && ring_pred(head->ring) == head->ring)
+ htable_delete(head->cache->endp_cache, head->parent_key, myfree);
+
+ /*
+ * Destroy the endpoint->session binding.
+ */
+ if (endp->fd >= 0 && close(endp->fd) != 0)
+ msg_warn("%s: close(%d): %m", myname, endp->fd);
+ myfree(endp->endp_prop);
+
+ myfree((void *) endp);
+}
+
+/* scache_multi_expire_endp - event timer call-back */
+
+static void scache_multi_expire_endp(int unused_event, void *context)
+{
+ SCACHE_MULTI_ENDP *endp = (SCACHE_MULTI_ENDP *) context;
+
+ scache_multi_drop_endp(endp, BOTTOM_UP);
+}
+
+/* scache_multi_free_endp - hash table destructor call-back */
+
+static void scache_multi_free_endp(void *ptr)
+{
+ SCACHE_MULTI_HEAD *head = (SCACHE_MULTI_HEAD *) ptr;
+ SCACHE_MULTI_ENDP *endp;
+ RING *ring;
+
+ /*
+ * Delete each endpoint->session binding in the list, then delete the
+ * list head. Note: this changes the list, so we must iterate carefully.
+ */
+ while ((ring = ring_succ(head->ring)) != head->ring) {
+ endp = RING_TO_MULTI_ENDP(ring);
+ scache_multi_drop_endp(endp, TOP_DOWN);
+ }
+ myfree((void *) head);
+}
+
+/* scache_multi_save_endp - save endpoint->session binding */
+
+static void scache_multi_save_endp(SCACHE *scache, int ttl,
+ const char *endp_label,
+ const char *endp_prop, int fd)
+{
+ const char *myname = "scache_multi_save_endp";
+ SCACHE_MULTI *sp = (SCACHE_MULTI *) scache;
+ SCACHE_MULTI_HEAD *head;
+ SCACHE_MULTI_ENDP *endp;
+
+ if (ttl < 0)
+ msg_panic("%s: bad ttl: %d", myname, ttl);
+
+ /*
+ * Look up or instantiate the list head with the endpoint name.
+ */
+ if ((head = (SCACHE_MULTI_HEAD *)
+ htable_find(sp->endp_cache, endp_label)) == 0) {
+ head = (SCACHE_MULTI_HEAD *) mymalloc(sizeof(*head));
+ ring_init(head->ring);
+ head->parent_key =
+ htable_enter(sp->endp_cache, endp_label, (void *) head)->key;
+ head->cache = sp;
+ }
+
+ /*
+ * Add the endpoint->session binding to the list. There can never be a
+ * duplicate, because each session must have a different file descriptor.
+ */
+ endp = (SCACHE_MULTI_ENDP *) mymalloc(sizeof(*endp));
+ endp->head = head;
+ endp->fd = fd;
+ endp->endp_prop = mystrdup(endp_prop);
+ ring_prepend(head->ring, endp->ring);
+ sp->sess_count++;
+
+ /*
+ * Make sure this binding will go away eventually.
+ */
+ event_request_timer(scache_multi_expire_endp, (void *) endp, ttl);
+
+ if (msg_verbose)
+ msg_info("%s: endp_label=%s -> endp_prop=%s fd=%d",
+ myname, endp_label, endp_prop, fd);
+}
+
+/* scache_multi_find_endp - look up session for named endpoint */
+
+static int scache_multi_find_endp(SCACHE *scache, const char *endp_label,
+ VSTRING *endp_prop)
+{
+ const char *myname = "scache_multi_find_endp";
+ SCACHE_MULTI *sp = (SCACHE_MULTI *) scache;
+ SCACHE_MULTI_HEAD *head;
+ SCACHE_MULTI_ENDP *endp;
+ RING *ring;
+ int fd;
+
+ /*
+ * Look up the list head with the endpoint name.
+ */
+ if ((head = (SCACHE_MULTI_HEAD *)
+ htable_find(sp->endp_cache, endp_label)) == 0) {
+ if (msg_verbose)
+ msg_info("%s: no endpoint cache: endp_label=%s",
+ myname, endp_label);
+ return (-1);
+ }
+
+ /*
+ * Use the first available session. Remove the session from the cache
+ * because we're giving it to someone else.
+ */
+ if ((ring = ring_succ(head->ring)) != head->ring) {
+ endp = RING_TO_MULTI_ENDP(ring);
+ fd = endp->fd;
+ endp->fd = -1;
+ vstring_strcpy(endp_prop, endp->endp_prop);
+ if (msg_verbose)
+ msg_info("%s: found: endp_label=%s -> endp_prop=%s fd=%d",
+ myname, endp_label, endp->endp_prop, fd);
+ scache_multi_drop_endp(endp, BOTTOM_UP);
+ return (fd);
+ }
+ if (msg_verbose)
+ msg_info("%s: not found: endp_label=%s", myname, endp_label);
+ return (-1);
+}
+
+/* scache_multi_drop_dest - delete destination->endpoint binding */
+
+static void scache_multi_drop_dest(SCACHE_MULTI_DEST *dest, int direction)
+{
+ const char *myname = "scache_multi_drop_dest";
+ SCACHE_MULTI_HEAD *head;
+
+ if (msg_verbose)
+ msg_info("%s: dest_prop=%s endp_label=%s",
+ myname, dest->dest_prop, dest->endp_label);
+
+ /*
+ * Stop the timer.
+ */
+ event_cancel_timer(scache_multi_expire_dest, (void *) dest);
+
+ /*
+ * In bottom-up mode, remove the list head from the destination hash when
+ * the list becomes empty. Otherwise, remove the destination->endpoint
+ * binding from the list.
+ */
+ ring_detach(dest->ring);
+ head = dest->head;
+ if (direction == BOTTOM_UP && ring_pred(head->ring) == head->ring)
+ htable_delete(head->cache->dest_cache, head->parent_key, myfree);
+
+ /*
+ * Destroy the destination->endpoint binding.
+ */
+ myfree(dest->dest_prop);
+ myfree(dest->endp_label);
+
+ myfree((void *) dest);
+}
+
+/* scache_multi_expire_dest - event timer call-back */
+
+static void scache_multi_expire_dest(int unused_event, void *context)
+{
+ SCACHE_MULTI_DEST *dest = (SCACHE_MULTI_DEST *) context;
+
+ scache_multi_drop_dest(dest, BOTTOM_UP);
+}
+
+/* scache_multi_free_dest - hash table destructor call-back */
+
+static void scache_multi_free_dest(void *ptr)
+{
+ SCACHE_MULTI_HEAD *head = (SCACHE_MULTI_HEAD *) ptr;
+ SCACHE_MULTI_DEST *dest;
+ RING *ring;
+
+ /*
+ * Delete each destination->endpoint binding in the list, then delete the
+ * list head. Note: this changes the list, so we must iterate carefully.
+ */
+ while ((ring = ring_succ(head->ring)) != head->ring) {
+ dest = RING_TO_MULTI_DEST(ring);
+ scache_multi_drop_dest(dest, TOP_DOWN);
+ }
+ myfree((void *) head);
+}
+
+/* scache_multi_save_dest - save destination->endpoint binding */
+
+static void scache_multi_save_dest(SCACHE *scache, int ttl,
+ const char *dest_label,
+ const char *dest_prop,
+ const char *endp_label)
+{
+ const char *myname = "scache_multi_save_dest";
+ SCACHE_MULTI *sp = (SCACHE_MULTI *) scache;
+ SCACHE_MULTI_HEAD *head;
+ SCACHE_MULTI_DEST *dest;
+ RING *ring;
+ int refresh = 0;
+
+ if (ttl < 0)
+ msg_panic("%s: bad ttl: %d", myname, ttl);
+
+ /*
+ * Look up or instantiate the list head with the destination name.
+ */
+ if ((head = (SCACHE_MULTI_HEAD *)
+ htable_find(sp->dest_cache, dest_label)) == 0) {
+ head = (SCACHE_MULTI_HEAD *) mymalloc(sizeof(*head));
+ ring_init(head->ring);
+ head->parent_key =
+ htable_enter(sp->dest_cache, dest_label, (void *) head)->key;
+ head->cache = sp;
+ }
+
+ /*
+ * Look up or instantiate the destination->endpoint binding. Update the
+ * expiration time if this destination->endpoint binding already exists.
+ */
+ RING_FOREACH(ring, head->ring) {
+ dest = RING_TO_MULTI_DEST(ring);
+ if (strcmp(dest->endp_label, endp_label) == 0
+ && strcmp(dest->dest_prop, dest_prop) == 0) {
+ refresh = 1;
+ break;
+ }
+ }
+ if (refresh == 0) {
+ dest = (SCACHE_MULTI_DEST *) mymalloc(sizeof(*dest));
+ dest->head = head;
+ dest->endp_label = mystrdup(endp_label);
+ dest->dest_prop = mystrdup(dest_prop);
+ ring_prepend(head->ring, dest->ring);
+ }
+
+ /*
+ * Make sure this binding will go away eventually.
+ */
+ event_request_timer(scache_multi_expire_dest, (void *) dest, ttl);
+
+ if (msg_verbose)
+ msg_info("%s: dest_label=%s -> dest_prop=%s endp_label=%s%s",
+ myname, dest_label, dest_prop, endp_label,
+ refresh ? " (refreshed)" : "");
+}
+
+/* scache_multi_find_dest - look up session for named destination */
+
+static int scache_multi_find_dest(SCACHE *scache, const char *dest_label,
+ VSTRING *dest_prop,
+ VSTRING *endp_prop)
+{
+ const char *myname = "scache_multi_find_dest";
+ SCACHE_MULTI *sp = (SCACHE_MULTI *) scache;
+ SCACHE_MULTI_HEAD *head;
+ SCACHE_MULTI_DEST *dest;
+ RING *ring;
+ int fd;
+
+ /*
+ * Look up the list head with the destination name.
+ */
+ if ((head = (SCACHE_MULTI_HEAD *)
+ htable_find(sp->dest_cache, dest_label)) == 0) {
+ if (msg_verbose)
+ msg_info("%s: no destination cache: dest_label=%s",
+ myname, dest_label);
+ return (-1);
+ }
+
+ /*
+ * Search endpoints for the first available session.
+ */
+ RING_FOREACH(ring, head->ring) {
+ dest = RING_TO_MULTI_DEST(ring);
+ fd = scache_multi_find_endp(scache, dest->endp_label, endp_prop);
+ if (fd >= 0) {
+ vstring_strcpy(dest_prop, dest->dest_prop);
+ return (fd);
+ }
+ }
+ if (msg_verbose)
+ msg_info("%s: not found: dest_label=%s", myname, dest_label);
+ return (-1);
+}
+
+/* scache_multi_size - size of multi-element cache object */
+
+static void scache_multi_size(SCACHE *scache, SCACHE_SIZE *size)
+{
+ SCACHE_MULTI *sp = (SCACHE_MULTI *) scache;
+
+ size->dest_count = sp->dest_cache->used;
+ size->endp_count = sp->endp_cache->used;
+ size->sess_count = sp->sess_count;
+}
+
+/* scache_multi_free - destroy multi-element cache object */
+
+static void scache_multi_free(SCACHE *scache)
+{
+ SCACHE_MULTI *sp = (SCACHE_MULTI *) scache;
+
+ htable_free(sp->dest_cache, scache_multi_free_dest);
+ htable_free(sp->endp_cache, scache_multi_free_endp);
+
+ myfree((void *) sp);
+}
+
+/* scache_multi_create - initialize */
+
+SCACHE *scache_multi_create(void)
+{
+ SCACHE_MULTI *sp = (SCACHE_MULTI *) mymalloc(sizeof(*sp));
+
+ sp->scache->save_endp = scache_multi_save_endp;
+ sp->scache->find_endp = scache_multi_find_endp;
+ sp->scache->save_dest = scache_multi_save_dest;
+ sp->scache->find_dest = scache_multi_find_dest;
+ sp->scache->size = scache_multi_size;
+ sp->scache->free = scache_multi_free;
+
+ sp->dest_cache = htable_create(1);
+ sp->endp_cache = htable_create(1);
+ sp->sess_count = 0;
+
+ return (sp->scache);
+}
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